1. Field of Invention
The invention relates to an ink jet printer that performs printing by ejecting ink from a print head, and particularly to an ink jet printer of an ink tube supply type where ink is supplied from an ink tank storing ink to be ejected to a print head through ink supply tubes.
2. Description of Related Art
As a conventionally known ink jet printer of ink tube supply type, there is an ink jet printer disclosed in Japanese Laid-Open Patent Publication No. 59-73953.
This ink jet printer designated by the numeral 20 is shown in FIG. 5. FIG. 5 is a perspective view showing the ink jet printer 20 in schematic form. The ink jet printer 20 includes a print head unit 21, a platen roller 22, a carriage 23, an ink tank 24, an ink tube 25, a signal input line 26, and guide rods 27.
The print head unit 21 is equipped with a print head having ink nozzles from which ink is ejected to perform printing onto a paper sheet based on a signal sent via the signal input line 26. The print head unit 21 receives a supply of ink from the ink tank 24 via the ink tube 25. The print head unit 21 is installed on the carriage 23, which is attached to a belt. The belt is looped around a roller attached to a motor. Thus, when the motor runs, the belt is driven, which allows the carriage 23 with the print head unit 21 to move for whatever distance the belt is driven.
The guide rods 27 are slidably inserted into the carriage 23 and support the carriage 23 for movement. Thus, the print head unit 21 installed on the carriage 23 can reciprocate in a direction parallel to the guide rods 27, that is, in the direction of the length of the platen roller 22.
In the ink jet printer of tube supply type, when the carriage equipped with the print head performs a printing operation while moving reciprocally, the ink in the ink tube undergoes acceleration, causing pressure waves that propagate in the ink toward the print head. The above-described printer is structured to absorb the pressure waves generated in the ink by placing an air-filled damper between the tubes.
On the other hand, to hold printing quality in condition, the ink jet printer needs to maintain a constant state of ink to be ejected from the ink nozzles. To maintain the state of ink to be ejected, a meniscus (curved surface) is formed on the surface of the ink at the end of each of the ink nozzles. As the meniscus is formed by, for example, causing a negative pressure in the ink to be supplied to the nozzles within a specified range, the pressure to supply the ink is kept constant, always producing the meniscus with the same shape. Thus, the ink to be ejected is maintained under a certain condition.
However, when the pressure waves propagating toward the print head are generated in the ink due to acceleration imported to the ink, the negative pressure applied to the nozzles is changed and the meniscuses are destroyed. Therefore, the ink to be ejected can not be maintained under a constant condition, affecting printing quality.
The invention provides an ink jet printer that can efficiently absorb pressure waves generated in ink passages during printing.
Considering the foregoing, one aspect of the invention involves an ink jet printer that includes a print head that performs printing on a recording medium by ejecting ink from an ink nozzle; a carriage on which the print head is mounted that moves along the recording medium; an ink tank that is provided separately from the carriage and stores ink to be supplied to the print head; an ink tube that is connected to the ink tank to supply ink from the ink tank; an ink chamber that is mounted on the carriage and connected to the print head to store ink supplied from the ink tank; and a connecting member that is connected to the ink tube and the ink chamber to supply ink supplied from the ink tank to the ink chamber, wherein the connecting member includes a passage to change a direction of flow of the ink supplied from the ink tube and a cushion to absorb pressure waves generated in the ink.
According to another aspect of the invention, the ink jet includes a print head that performs printing to a recording medium by ejecting ink from an ink nozzle; a carriage on which the print head is mounted that moves along the recording medium; an ink tank that is provided separately from the carriage and stores ink to be supplied to the print head; an ink tube that is connected to the ink tank to supply ink from the ink tank; an ink chamber that is mounted on the carriage and connected to the print head to store ink supplied from the ink tank; and a connecting member that includes an ink inflow port connected to the ink tube to take ink supplied from the ink tank and an ink outflow port connected to the ink chamber, wherein a cushion is provided at an extremity extending from an intersection of the ink inflow port and the ink outflow port in a direction the ink flows from the ink inflow port.